And net migration statistics should continue to be taken with a major dose of salt.

BBC: The truth behind UK migration figures

The Public Administration (9.30am) has a session on migration statistics which should not be nearly as dry as it sounds.

BBC: Week ahead in committees

The statisticians at the ONS still have high hopes that e-borders will one day be able to provide reliable migration statistics.

BBC: The truth behind UK migration figures

Ministers have been urged to remove foreign students from net migration statistics to allow the UK to continue to expand its share of the lucrative overseas student market.

BBC: UK Politics

And it said that the Office for National Statistics had made its migration statistics clearer, so that it was more easy for students to be identified in emigration flows "to give a more accurate measure of the contribution of students to overall net migration".

BBC: Foreign students to stay in migration figures

Some also think the statistics could reflect a migration of healthier women out of rural areas, leaving behind others who are too poor and unhealthy to relocate.

WSJ: Study Points to Declining Life Span for Some U.S. Women

Mr Johnson and other MPs are urging ministers to remove student visa statistics from the government's overall net migration target.

BBC: Mr Johnson with schoolchildren at Amity University

However, those statistics are not always perfect indicators of the economic effects migration has on a city.

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